Most jobs that come from the field arrive with no drawing. You have a broken, worn or discontinued part in your hand. That is not an obstacle.
Step one is a photo. Put a caliper or a ruler next to the part, shoot it from a few angles and send it over WhatsApp. That is usually enough to say whether the job is feasible.
Step two is measurement. We measure the part in the shop and derive the critical dimensions and tolerances. On a worn part the real work is estimating the original dimension correctly — knowing the mating part helps a great deal here.
Step three is the sample. One part is produced, you approve it, and only then does series production start.